What a terrible Pandora’s box has been opened and for what? Apart from climate change it is hard to think of a greater challenge faced by this island since the Great Famine of 1845. It is hard to be optimistic but we must remain determinedly so.
First, WWI. Tens of thousand of Irishmen died in that war. Somewhere in the range of 30,000 - 40,000 seems to be accepted among historians these days. 30,000+ Irishmen dead in a war. I would imagine that was challenging.
Then there was the War of Independence, the Irish Civil War and all the work that went into rebuilding Ireland afterwards. I'd guess that was fairly challenging.
Then there was WWII. Again, thousands of Irishmen died in the conflict and for a while the future of Europe hung by a fingernail. I would bet those were challenging times and worrying, right? I mean, the Nazis could have won, which would have been an issue if Ireland was in Europe. If.
There were some significantly challenging times post-War too, some that were probably about as challenging as life post-Brexit will be. And there was that whole Cold War thing when life on Earth itself seemed to be at risk.
No, life post-Brexit will not be the greatest "challenge faced by this island since the Great Famine." Not even close.